GB1263699A - Improvements in or relating to measuring devices - Google Patents

Abstract

1,263,699. Measuring surface roughness electrically; peak and mean voltage measurement. RANK ORGANISATION Ltd. May 14, 1969 [May 16, 1968], No.23342/68. Headings G1N and G1U. The condition of a surface is sensed by a stylus producing electrical signals corresponding to the peaks and valleys which are fed to storage capacitors and subsequently combined to determine the mean peak and valley values. As shown Fig. 1, a stylus 11 is driven by a shaft 14 to traverse a test surface 12, the variations in level being converted by transducer 13 to electrical signals which are fed via amplifier 23, diode 29 and wiper contact 16 successively to capacitors 10. The wiper 16 is geared to shaft 14 so that each capacitor 10 is associated with a unit length of surface 12 and is charged to a voltage representing the peak value of that length. The wiper 16 is followed by a conductive segment 24 which progressively inter-connects the capacitors 10 to enable the mean peak to be indicated on a meter 25. A similar bank fed through a reversed diode enables the mean valley to be indicated on a meter. The switching may be effected electronically by transistors Q 1 -Q n Fig. 4 which are fed consecutively with a positive base potential to make one conductive whilst the remainder are fed with a negative base potential to leave them open. Thus, initially transistor Q 1 is made conductive with V 1 positive and capacitor C 1 is charged to the peak value of the measuring signal V o , which is also fed via cathode follower valve E 1 , to meter M. During this period all the other transistor base voltages V 2 -V n are negative. After a desired interval V 1 is made negative and V 2 positive, when M indicates the peak value of the second section of the test surface. This is continued throughout the series of transistors Q 1 -Q n , when switch S is opened and all the transistors Q 1 -Q n switched on, when meter M indicates the mean value of the peaks. Transistor Q c is then made conductive to discharge all the capacitors C 1 -C n , switch 5 is closed and the cycle repeated. The switching voltages V 1 etc. may be obtained from an open ring counter driven by a multi-vibrator.